const yuvBehavior = Behavior({
  methods: {
    initShader() {
      const gl = this.gl = this.renderer.getContext()
      const currentProgram = gl.getParameter(gl.CURRENT_PROGRAM)
      const vs = `
        attribute vec2 a_position;
        attribute vec2 a_texCoord;
        uniform mat3 displayTransform;
        varying vec2 v_texCoord;
        void main() {
          vec3 p = displayTransform * vec3(a_position, 0);
          gl_Position = vec4(p, 1);
          v_texCoord = a_texCoord;
        }
      `
      const fs = `
        precision highp float;

        uniform sampler2D y_texture;
        uniform sampler2D uv_texture;
        varying vec2 v_texCoord;
        void main() {
          vec4 y_color = texture2D(y_texture, v_texCoord);
          vec4 uv_color = texture2D(uv_texture, v_texCoord);

          float Y, U, V;
          float R ,G, B;
          Y = y_color.r;
          U = uv_color.r - 0.5;
          V = uv_color.a - 0.5;
          
          R = Y + 1.402 * V;
          G = Y - 0.344 * U - 0.714 * V;
          B = Y + 1.772 * U;
          
          gl_FragColor = vec4(R, G, B, 1.0);
        }
      `
      const vertShader = gl.createShader(gl.VERTEX_SHADER)
      gl.shaderSource(vertShader, vs)
      gl.compileShader(vertShader)

      const fragShader = gl.createShader(gl.FRAGMENT_SHADER)
      gl.shaderSource(fragShader, fs)
      gl.compileShader(fragShader)

      const program = this._program = gl.createProgram()
      this._program.gl = gl
      gl.attachShader(program, vertShader)
      gl.attachShader(program, fragShader)
      gl.deleteShader(vertShader)
      gl.deleteShader(fragShader)
      gl.linkProgram(program)
      gl.useProgram(program)

      const uniformYTexture = gl.getUniformLocation(program, 'y_texture')
      gl.uniform1i(uniformYTexture, 5)
      const uniformUVTexture = gl.getUniformLocation(program, 'uv_texture')
      gl.uniform1i(uniformUVTexture, 6)

      this._dt = gl.getUniformLocation(program, 'displayTransform')
      gl.useProgram(currentProgram)
    },
    initVAO() {
      const gl = this.renderer.getContext()
      const ext = gl.getExtension('OES_vertex_array_object')
      this.ext = ext

      const currentVAO = gl.getParameter(gl.VERTEX_ARRAY_BINDING)
      const vao = ext.createVertexArrayOES()

      ext.bindVertexArrayOES(vao)

      const posAttr = gl.getAttribLocation(this._program, 'a_position')
      const pos = gl.createBuffer()
      gl.bindBuffer(gl.ARRAY_BUFFER, pos)
      gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([1, 1, -1, 1, 1, -1, -1, -1]), gl.STATIC_DRAW)
      gl.vertexAttribPointer(posAttr, 2, gl.FLOAT, false, 0, 0)
      gl.enableVertexAttribArray(posAttr)
      vao.posBuffer = pos

      const texcoordAttr = gl.getAttribLocation(this._program, 'a_texCoord')
      const texcoord = gl.createBuffer()
      gl.bindBuffer(gl.ARRAY_BUFFER, texcoord)
      gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([1, 1, 0, 1, 1, 0, 0, 0]), gl.STATIC_DRAW)
      gl.vertexAttribPointer(texcoordAttr, 2, gl.FLOAT, false, 0, 0)
      gl.enableVertexAttribArray(texcoordAttr)
      vao.texcoordBuffer = texcoord

      ext.bindVertexArrayOES(currentVAO)
      this._vao = vao
    },
    initGL() {
      this.initShader()
      this.initVAO()
    },
    renderGL(frame) {
      const gl = this.renderer.getContext()
      gl.disable(gl.DEPTH_TEST)
      const {
        yTexture,
        uvTexture
      } = frame.getCameraTexture(gl, 'yuv')
      const displayTransform = frame.getDisplayTransform()
      if (yTexture && uvTexture) {
        const currentProgram = gl.getParameter(gl.CURRENT_PROGRAM)
        const currentActiveTexture = gl.getParameter(gl.ACTIVE_TEXTURE)
        const currentVAO = gl.getParameter(gl.VERTEX_ARRAY_BINDING)

        gl.useProgram(this._program)
        this.ext.bindVertexArrayOES(this._vao)

        gl.uniformMatrix3fv(this._dt, false, displayTransform)
        gl.pixelStorei(gl.UNPACK_ALIGNMENT, 1)

        gl.activeTexture(gl.TEXTURE0 + 5)
        const bindingTexture5 = gl.getParameter(gl.TEXTURE_BINDING_2D)
        gl.bindTexture(gl.TEXTURE_2D, yTexture)

        gl.activeTexture(gl.TEXTURE0 + 6)
        const bindingTexture6 = gl.getParameter(gl.TEXTURE_BINDING_2D)
        gl.bindTexture(gl.TEXTURE_2D, uvTexture)

        gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4)

        gl.bindTexture(gl.TEXTURE_2D, bindingTexture6)
        gl.activeTexture(gl.TEXTURE0 + 5)
        gl.bindTexture(gl.TEXTURE_2D, bindingTexture5)

        gl.useProgram(currentProgram)
        gl.activeTexture(currentActiveTexture)
        this.ext.bindVertexArrayOES(currentVAO)
      }
    },
  },
})

export default yuvBehavior
